CARBON-ISOTOPE COMPOSITION OF SEDIMENTS FROM THE GULF-OF-PAPUA

Rivers draining into the Gulf of Papua (GOP) from the Papua New Guinea mainland deliver approximately 340 x 10(6) t yr(-1) of sediment to th e marine environment. The terrestrially derived sediment contains 1.1 +/- 0.2% particulate organic carbon with a carbon-isotope composition of -26.5 +/- 0.2 parts per thousand, and amounts to 3.7 +/- 0.7 x 10(6 ) t yr(-1). The carbon-isotope composition of sediments in the Gulf of Papua indicates that 40% of the sediment cover contains 75% or more t errestrially derived carbon. Suspended sediments that are transported beyond the delta complex of the Fly River are transported north and no rthwest, augmented by sediments from other rivers along the coast of t he GOP. The carbon-isotope results suggest that a significant quantity of terrestrially derived sediment escapes from the GOP, either along the coastlines to east and west or into the deep ocean via the Moresby and Pandora troughs. Little sediment travels south onto the Great Bar rier Reef shelf. Extrapolating the results from this study to the regi on of Oceania suggests a total flux of particulate organic carbon to t he world's oceans from the islands of Oceania of similar to 90 x 10(6) t yr(-1) or twice the flux of riverine POC from the major rivers of N orth America, South America, and Africa combined. While such a calcula tion must be considered illustrative only, the similar tectonic, geomo rphologic, and climatic features of the islands of Oceania suggest tha t the calculation is unlikely to be grossly in error and that the rive rs of Oceania therefore represent a major but poorly documented source of sediment and organic carbon to the global ocean.